trigger OpportunityMonthFollowTrigger on OpportunityMonthFollow__c(after insert , after update,after delete  ) {
    

    if(Trigger.isAfter && (Trigger.isUpdate || Trigger.isInsert ))OpportunityMonthFollowHandler.lastFollowup(Trigger.new,Trigger.oldMap);
     if(Trigger.isAfter && trigger.isDelete )OpportunityMonthFollowHandler.lastFollowup(Trigger.old,new Map<Id,OpportunityMonthFollow__c>());

}